The present invention relates to a grinding wheel having an adjustable axial dimension. Particularly, the present invention is directed to such a grinding wheel including a wheel supporting body and an abrasive material covering at least a circumferential surface of the wheel supporting body, radially outer portions of the axially spaced side or end surfaces, and transitional areas between such circumferential and side surfaces. Such abrasive material covering is of diamond, crystalline boron nitride (CBN) or a similar super-hard bound adhesive for grinding operations wherein stress is generated on or imparted to the side surfaces of the grinding wheel.
There are known various types of grinding operations wherein grinding is achieved not only by the circumferential surface of the grinding wheel or by inclined or beveled circumferential surfaces thereof, but also wherein grinding must be achieved by portions of the axially spaced side or end surfaces of the grinding wheel. A typical example is the grinding or placement of crank shafts for engines, wherein in addition to the ground surfaces necessary for fastening of connecting rods or to the ground surfaces for mounting the crank shaft in the engine block, there also must be achieved grinding on both sides of transitional radii and on both sides of bearing shoulders in directions of 90.degree. to the axial direction or placement of the crank shaft. To achieve such side ground surfaces, the grinding wheel must have a precisely calibrated width, i.e. axial dimension. The side surfaces of the grinding wheel are strongly stressed during such side grinding operations, since the shoulder height must be cut in or ground as quickly as possible. The resultant abrasion on the transition points from the circumferential surface to the radially extending side surfaces of the grinding wheel therefore must be frequently replaced and renewed for grinding wheels formed conventionally totally of corundum or silicone carbide. This conventionally is achieved by strong trimming or dressing of the circumference of the grinding wheel. This however leads to a great waste of the abrasive material of the grinding wheel.
With super-hard grinding materials, for example diamond or cubic crystalline boron nitride (CBN), it is not necessary for the entire grinding wheel to be formed of the abrasive. Rather, a surface covering or layer of a few millimeters of the particular super-hard bound grinding material is applied to the circumferential surface of the wheel, i.e. specifically on a supporting body thereof, and to areas of the side surfaces of the wheel supporting body. This is achieved, and indeed necessary, for economic reasons due to the high cost of such high quality abrasive materials. However, this also is possible for technical reasons due to the fact that, based on past experience, a greater grinding capacity and a longer edge life is possible between trimming or dressing cycles when employing such harder abrasives. With diamond or CBN-layered grinding wheels, for example, the transitional edge area between the circumferential and side surfaces will have a service life of up to one thousand times greater between dressing or trimming operations than is possible with more conventional materials. Also, the dressing or trimming operations on the circumferential surface, when performed, amount to only a few .mu.m. Thus, the wearability of this type of abrasive material can be limited to only a few millimeters.
However, there exists an unsolved problem with the use of this type of grinding wheel with a surface covering of a super-hard abrasive in a grinding operation with large stress applied to the side surfaces of the grinding wheel. Thus, since the dressing process on the surface of the grinding wheel amounts to only a few .mu.m per treatment, the transition point between the circumferential surface and the side surfaces of the grinding wheel is not sufficiently renewed. The grinding wheel therefore essentially becomes narrower with every dressing or trimming operation. As a result, the accuracy of a side grinding operation is varied. For example, with the placement grinding discussed above for a crank shaft, the width of such side grinding operation is changed by an undesirable amount.